The modulator in this disclosure is not restricted by the usual limitations of small aperture, low efficiency, and restricted spectral regions of operation common to laser modulators currently under development for optical communications systems, laser radar, and optical data processing. Due to their small linear and angular apertures, and high absorption at wavelengths longer than 1.5 microns, modulators now being tried in visible range laser systems are unsuitable for taking advantage of the powerful CO.sub.2 laser which operate at 10.6 microns. These modulators depend upon bulk properties of materials whereas the present modulator works on a different principle. The proposed modulator utilizes the optical properties of narrow absorption lines induced into the material by doping with suitable impurities or due to the molecular structure of the material.